Receiving circuit for the elimination



Oct. 28, 192 4. v I 1,513,223

j F. CONRAD RECEIVING CIRCUIT FOR THE ELIMINATION OF STATIC DISTURBANCBS'F11ed, .0ct. 17, 1918 INVENTOR WITNESSES:

TTORNEY Patented Oct. 28, 1924.

UNITED STATES PATENT OFFICE.

FRANK CONRAD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR- T WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

RECEIVING CIRCUIT FOR THE ELIMINATION 01* STATIC DISTURBANGES.

Application filed October 17, 1918. Serial No. 258,530.

ple and effective means whereby interfer-.

ence, particularly that known as static, may be largely eliminated, atthe same time permitting the readyreceipt of transmitted impulses.

The single figure of the accompanying drawing is a diagram of a wirelessreceiving circuit embodying a preferred form of my invention.

In the wireless transmission of intelligence, it is well known that thereceipt of transmitted impulses is frequently seriously disturbed bystatic charges produced upon the antenna by the passage of windthereoyer. these static charges flowing to ground through the receivingapparatus. Qimilarly. the passage of elec-trostatically char ed cloudsover the antenna attracts or repels chargesfrom the ground, these alsopassing through the receiving apparatus and confusing the operator.

I find that the static charges and static induction in antennae ofdifferent heights is substantially the same, whereas the intensity ofthe impulse set up in an antennaby incoming signals varies with theheight. being much stronger for an. antenna of considerable height thanfor one of moderate height. I make use of this phenomenon in eliminatingthe disturbing effects of static electricity by employing two antennaefor the receipt of messages. these antennae being so associated withreceiving apparatus that the substantially equal charges impartedthereto by static influences cancel each other within the receivingapparatus. thus being rendered imperceptible to the operator. Theunequal amounts of energy imparted to the antenna by incoming impulsesfail to cancel each other and thus a residual eifect is imparted in thereceiving apparatus which may be amplified if desirable in order torender it more clearly perceptible to the operator.

Referring to the drawing for a more detailed understanding of myinvention, I show a relatively l'iigh wireless antenna at l and arelatively low antenna at 2. These antennas are shown of the flat-toptype but it is to be understood that any antennae of the open-circuitkind may be used. Some antennae, usually in the form of a coil, actwholly, or at least largely, by the change in flux through them which iscaused by an arriving ether wave. Other antennae act wholly or mainly invirtue of the electrostatic changes which accompany such a wave. I haveused the term open-circuit antenna herein to designate any form ofantenna belonging in the latter class. A receiving transformer is shownat 3 and the antenna 1 is connected to one end of a primary widing 4thereof. whereas the antenna 2 is connected to the other end thereof. An

adjustable tap 5 is provided at an intermediate point in the primarywinding 4 and is grounded at 6. The secondary winding 7 of thetransformer 3 is connected, to a recei ing circuit of usual form.

Assuming equal sizes for the two antennae. the amounts of energyreceived therein are substantially equal with undesired staticdisturbances but are quite unequal with trans mitted impulses, the highantenna developing much more energy in the latter case. The point ofattachment 5 is, under these conditions, placed at substantially the midpoint of the winding 42, so that, with a given static impulse, theupwardly flowing current in the lower half of the winding 4 magneticallyneutralizes the downwardly flowing; current in the upper half of thiswinding. the current of both antennae flowing to ground though the tap 5and the lead 6. As a result, with a static impulse, no flux is developed in the transformer 3, and consequently, no electromotive forceis produced in the winding 7 and no effect is produced in the localreceiving circuit.

Turning now to the effect upon the receipt of a transmitted impulse, thecurrent flowing from the antenna 1 is much larger than that flowing fromthe antenna 2 and, therefore, the magnetomotiye force developed in thelower half of the winding 4 is greater than that developed in the upperhalf thereof. As a consequence, flux is developed in the core of thetransformer 3 which traverse the secondary winding 7 setting up currenflow in the local receiving circuit. The arrivingsignal produces agreater effect on the antenna 1, not only because a higher antennapossesses a' better receiving" capacity, but also because, being fartherfrom roofs, trees and the like, it is more exposed to the action of thearriving wave.

It is obvious that the resultant impulse at the receiving instrument isconsiderably weaker than would be the case were this apparatus connectedto a single antenna, but any well-known type of amplifier may beemployed to increase the magnitude of the signals so that they shall bereadily audible.

While I have shown my invention in its preferred form, it will beobvious to those skilled in the art that it is susceptible of stillother minor changes and modifications.

without departing from the spirit thereof and desire, therefore, thatonly such limitations shall be placed thereupon as are imposed by theprior art or are specifically set forth in the appended claims. I claimas my invention: A

1. In a wireless receiving circuit, the com bination with two antennaeof different heights, of a common local receiving circuit differentiallyconnected to said two antennae and susceptible of adjustment so that theenergy received on one antenna from a static impulse cancels the energyreceived upon the other antenna, and so that similar cancellation is noteffected with incoming transmitted impulses.

2. In a Wireless receiving circuit, the combination with two antennae ofdifferent heights, of a common receiving transformer having its primarywinding connected tween said antennae, a local. receiving circuitdynamically interlinked therewith, and an adjustable connection from anintermediate point in said transformer primary winding to ground.

4. Inradio signaling apparatus, an antenna system havingassociatedportions an ranged at different elevations butat tially thesame distance from the source of signals to be received, and means fordetecting signals including means for balancing out the effects ofstatic disturbances.

5. In a signal receiving system, two adjacent flat-top antennae ofdifferent height.

. 6. In a signal receiving system, two adja-. cent flat-top antennae ofdifferent height and signal translating means controlled by thedifference of energy between said antennae.

In testimony whereof, I have hereunto subscribed my name this 25th dayof Sept. 1918. i

FRANK CONRAD-

